Pairing plc devices

ABSTRACT

A power line communication device includes a power line communication unit, a sensor to sense a physical connection to a second power line communication device other than via a powerline medium and a pairing unit to receive an indication of a physical connection between the power line communication device and the second power line communication device and to initiate a pairing process with the second power line communication device. A method of pairing communication devices which communicate along a non-data-cable medium includes sensing a data cable connection with a second device, entering an appropriate pairing state upon sensing the data cable connection, the pairing state being either an add device state or a join device state and performing pairing with the second device along the non-data-cable connection.

FIELD OF THE INVENTION

The present invention relates to power line communication devicesgenerally and, in particular, to elements which enable a device to joina network.

BACKGROUND OF THE INVENTION

Power line networks are becoming increasingly common. Such networks areformed of devices (known as power line communication (PLC) devices)which communicate digital data over the in-building power lines and, assuch, reduce the amount of wiring in a building.

There are a number of standards for power line networks, the most recentbeing the G.hn standard. Each one defines how the devices should operateand communicate with one another and with external networks. Since powerlines extend beyond the reach of a single premises, thereby enablingneighboring networks to hear one another, it is imperative that thedevices know to which network they belong. To this end, a “pairing”process was designed, in which a new PLC device “pairs” with another PLCdevice that is connected to the network, and receives an encryption keyfrom that device. The current pairing mechanism requires that theencryption key be exchanged within a predefined time period (usually 2minutes) from the time that the pairing is initiated.

The pairing process is usually initiated by depressing a switch on thePLC device. Usually, the user is instructed to press the switch for 2seconds. A shorter or longer duration of the switch depression may notproperly enable the pairing process.

Once the pairing process is initiated in the first PLC device, the userneeds to repeat the process in the other devices on the network within apredefined time period—usually within 2 minutes. PLC devices that areinstalled in remote locations of the building may require more time toaccess and the allowed time period for completing the pairing processmay not be sufficient.

Furthermore, once the pairing process is initialized, the PLC devicewill share its encryption key with any other device on the network ifthe other device has been initialized for pairing during the allowedtime period. Thus, devices on neighboring networks that are withincommunication reach of the pairing device can retain the encryption keyif they also happen to be initialized to pair at the same time.

SUMMARY OF THE PRESENT INVENTION

There is provided, in accordance with a preferred embodiment of thepresent invention, a method of pairing power line communication devices.The method includes sensing a physical connection with a second device,where the physical connection is other than via a powerline medium,entering an appropriate pairing state upon sensing the physicalconnection, where the pairing state is either an add device state or ajoin device state and performing pairing with the second device.

Moreover, in accordance with a preferred embodiment of the presentinvention, the physical connection is a data cable.

Further, in accordance with a first preferred embodiment of the presentinvention, the sensing includes sensing the connection of the data cableand the connection of the second device also to the data cable.

Still further, in accordance with a first preferred embodiment of thepresent invention, the method also includes the device in the joindevice state passing an identifier to the device in the add state overthe cable and the device in the add state agreeing to the performingonly with a device having the identifier.

Alternatively, in accordance with a second preferred embodiment of thepresent invention, the physical connection is a pass through powerconnection.

Moreover, in accordance with a second preferred embodiment of thepresent invention, the entering includes each device sensing if thedevice is closer or further from a wall socket than another device anddevices not connected to the wall socket receiving a network key atleast from a device connected to the wall socket.

There is also provided, in accordance with a preferred embodiment of thepresent invention, a power line communication device. The deviceincludes a power line communication unit, a sensor to sense a physicalconnection to a second power line communication device other than via apowerline medium and a pairing unit to receive an indication of aphysical connection between the power line communication device and thesecond power line communication device and to initiate a pairing processwith the second power line communication device.

Moreover, in accordance with a preferred embodiment of the presentinvention, the sensor is an Ethernet link sensor and the physicalconnection is via an Ethernet cable.

Further, in accordance with a preferred embodiment of the presentinvention, the pairing unit includes a data unit to pass a deviceidentifier, if the device is in a join device state, or to receive adevice identifier if the device is in an add state along the Ethernetcable.

Alternatively, in accordance with a preferred embodiment of the presentinvention, the powerline communication device also has a pass-throughpower connection. In this embodiment, the sensor is an inner sensingunit at an inner location of the device to sense if the device isplugged in and an outer sensing unit at an outer location of the deviceto sense if a second power line communication device is plugged into thedevice. The power line communication unit includes a network key unit tocontrol a network key as a function of which of the switches isactivated.

Moreover, in accordance with a preferred embodiment of the presentinvention, the network key unit includes a receiver to receive a networkkey when the inner sensing unit is activated and a transmitter totransmit the network key when the outer sensing unit is activated.

Further, in accordance with a preferred embodiment of the presentinvention, the power line communication device also includes a socketand a plug, wherein the inner location is underneath a surface of thesocket and the outer location is underneath a surface of the plug.

Still further, in accordance with a preferred embodiment of the presentinvention, two or more units are connectable together.

Alternatively, in accordance with a preferred embodiment of the presentinvention, the sensing units are proximity sensors. For example, theymight be electrical proximity sensors, reed switches controllable bymagnets or micro switches depressed by mechanical pressure.

Further alternatively, the sensing units are transmission sensors. Forexample, they might be RFID units or coils that receive and transmit.

There is also provided, in accordance with a preferred embodiment of thepresent invention, a method of pairing communication devices whichcommunicate along a non-data-cable medium. The method includes sensing adata cable connection with a second device, entering an appropriatepairing state upon sensing the data cable connection, the pairing statebeing either an add device state or a join device state and performingpairing with the second device along the non-data-cable connection.

There is still further provided, in accordance with a preferredembodiment of the present invention, a method of pairing power linecommunication devices. The method includes having the devicesincorporated into pass-through devices, plugging a first pass-throughdevice into a wall socket and at least a second pass-through device intothe first device and unplugging the devices from the socket and fromeach other after pairing has occurred.

Moreover, in accordance with a preferred embodiment of the presentinvention, the plugging includes connecting the devices together priorto plugging the combination into the wall socket. Alternatively, theplugging includes connecting the devices one at a time.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter regarded as the invention is particularly pointed outand distinctly claimed in the concluding portion of the specification.The invention, however, both as to organization and method of operation,together with objects, features, and advantages thereof, may best beunderstood by reference to the following detailed description when readwith the accompanying drawings in which:

FIGS. 1A and 1B are isometric and schematic illustrations, respectively,of a prior art pass-through connector;

FIG. 2A is a schematic illustration of an improved pass-throughconnector, constructed and operative in accordance with a preferredembodiment of the present invention;

FIG. 2B is a circuit diagram illustration of a sensing unit for theconnector of FIG. 2A;

FIG. 3A is an isometric illustration of connecting together twopass-through connectors of FIG. 2A;

FIG. 3B is a schematic illustration of the two pass-through connectorsof FIG. 3A upon connection;

FIG. 3C is a schematic illustration of three connected pass-throughconnectors of FIG. 3A;

FIG. 4 is a flow chart illustration of a pairing process performed byeach of the connectors when connected together as in FIGS. 3B and 3C;

FIG. 5 is a schematic illustration of an alternative embodiment forpairing, utilizing a cable connection; and

FIG. 6 is a transmission diagram illustration showing a method ofutilizing the pairing elements of FIG. 5.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the figures have not necessarily been drawn to scale.For example, the dimensions of some of the elements may be exaggeratedrelative to other elements for clarity. Further, where consideredappropriate, reference numerals may be repeated among the figures toindicate corresponding or analogous elements.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the invention.However, it will be understood by those skilled in the art that thepresent invention may be practiced without these specific details. Inother instances, well-known methods, procedures, and components have notbeen described in detail so as not to obscure the present invention.

Applicants have realized that a physical connection between two powerline communication (PLC) devices may provide “hands-free pairing”. Thephysical connection may be any suitable type of connection. Inaccordance with a preferred embodiment of the present invention, thephysical connection may be provided by connecting together “pass-throughconnectors”. In accordance with an alternative preferred embodiment ofthe present invention, the physical connection may be provided by acable connection.

Reference is now made to FIGS. 1A and 1B, which illustrate an exemplaryPLC device 10 isometrically (FIG. 1A) and schematically (FIG. 1B).Device 10 may comprise a housing 12, a plug 14, an outlet 16, and a PLCunit 11. Via a data connector 15, PLC unit 11 may connect to a computingdevice 19 and may provide communication for computing device 19 withother PLC-connected devices across the power lines of the premises.

Device 10 may use plug 14 to connect to the power lines (for power andfor communication) via a wall socket (or power outlet) 18. Because thePLC device utilizes wall socket 18, many PLC devices provide additionaloutlet 16 (a “pass-through connection”) connected to a filter 13 toprovide filtered AC power to non-PLC devices. Additional outlet 16 mayhave a further advantage in that it may filter any noise caused by thenon-PLC device connected thereto, thereby keeping the noisy non-PLCdevice from adding noise to the power line network, which noise maydegrade the quality of communication over the power lines. Filter 13 maybe a low pass filter such that only the low AC power frequency (in therange of 50-60 Hz) may pass through it. As the PLC signals areconcentrated in frequencies above 2 MHz, the low AC power frequencyshould not affect them.

Applicants have realized that not only non-PLC devices may utilizeadditional outlet 16. A PLC unit may also be plugged into outlet 16, atleast temporarily, and this physical connection may be utilized for thepairing process.

Reference is now made to FIG. 2A, which details a pass-through PLCdevice 20, constructed and operative in accordance with a preferredembodiment of the present invention. PLC device 20 may comprise housing12, plug 14, outlet 16 and filter 15, as in device 10. In FIG. 2A, thePLC unit is labeled 22.

In accordance with a preferred embodiment of the present invention, PLCdevice 20 may also comprise a pairing circuit 24 and two sensing units25A and 25B. Sensing units 25 may detect proximity between two adjacentPLC devices 20 such that pairing circuit 24 may determine when two PLCdevices 20 are paired. As described in more detail hereinbelow, sensingunits 25 may also be located so as to indicate to pairing circuit 24which device 20 is closest to wall socket 18, since the inner device maybecome the master which will transfer the network key (stored in astorage unit 23) to the outer device. For example, the A location may benear a front surface of housing 12 close to outlet 16 and the B locationmay be near a back surface of housing 12 close to plug 14.

Sensing units 25 may be any suitable device which can sense proximity,such as electrical proximity sensors, reed switches controllable bymagnets or micro switches depressed by mechanical pressure (the lattermay stick out from housing 12 and may only be depressed when another PLCdevice 20 is pressed against it).

In another embodiment, sensing units may be capable of sensingtransmissions, such as RFID units or coils that receive and transmit.Such units may be set to respond only when they sense very strongtransmissions, such as only occur when two PLC units 22 are very closeto each other.

Reference is now made to FIG. 2B, which illustrates the elements ofpairing circuit 24 connected to sensing units 25A and 25B. Each sensingunit 25 may be serially connected to a resistor 27 and the twocombinations may be connected in parallel to each other, between aninput voltage V and ground. There may be two output signals, eachmeasuring the voltage level across one sensing unit 25.

Accordingly, pairing circuit 24 may provide a multi-mode output, whereone mode may indicate that sensing unit 25A has been activated, a secondmode may indicate that sensing unit 25B has been activated, a third modemay indicate that both sensing units 25 are not activated and a fourthmode may indicate that both sensing units are activated. Thus, pairingcircuit 24 may indicate to PLC unit 22 which a sensing unit 25, if any,has been activated.

Reference is now made to FIGS. 3A and 3B, which isometrically andschematically illustrate the pairing of two PLC units 20C and 20D, whenconnected to wall socket 18.

The embodiment of FIGS. 3A and 3B shows sensing units 25 each formed ofone micro switch 26 and one magnet 28. Micro switch 26A and magnet 28Amay be located in the A location, near a surface of housing 12 close tooutlet 16, and micro switch 26B and magnet 28B may be located in the Blocation, near a surface of housing 12 close to plug 14.

Micro switches 26 may be any suitable micro switches, such as Reedswitches (such as the Meder KSK-1A80 reed switches), which may close inthe presence of a magnet. Thus, as shown in FIGS. 3A and 3B, if a PLCdevice 20D were to be plugged into a PLC device 20C which is pluggedinto wall socket 18, the magnets 28 of one device 20 may affect themicro switches 26 of the other device 20. Since PLC device 20C may beplugged into wall socket 18, it may act as the master unit while PLCdevice 20D, plugged into PLC device 20C, may act as the slave unit.

In particular, the A magnet of the inner device (PLC device 20C in FIG.3B) may affect the B micro switch of the outer device (PLC device 20D inFIG. 3B) and the B magnet of the outer device may affect the A microswitch of the inner device. Thus, as shown in FIG. 3B, magnet 28A-C(i.e. magnet 28A of PLC device 20C) has closed micro switch 26B-D andmagnet 28B-D has closed micro switch 26A-C.

It will be appreciated that the A location may be set to be “under” theB location when two devices 20 are connected together. The A magnet 28may be placed so as to be under the B micro switch 26 and the B magnet28 may be placed so as to be “over” the A micro switch 26 when thedevices are connected together, such that the magnets 28 may stronglyaffect the micro switches 26.

Pairing circuit 24C on inner device 20C may determine that its microswitch 26A has been closed while pairing circuit 24D on outer device 20Dmay determine that its micro switch 26B has been closed.

It will be appreciated that the A location may indicate that the device20 may be the inner device while the B location may indicate that thedevice 20 may be the outer device. The present invention may utilizethis fact to perform the pairing operation.

Reference is now made to FIG. 3C which illustrates the option to pairmultiple devices by connecting multiple PLC devices to each other. Threedevices 20C, 20D and 20E are shown, connected 20E to 20D, 20D to 20C and20C to wall socket 18. Pairing circuit 24C may indicate that its switch26A is closed, pairing circuit 24D may indicate that both its switches26A and 26B are closed while pairing circuit 24E may indicate that itsswitch 26B is closed.

Given these indications, device 20C (whose pairing circuit 24C indicatedthat only switch 26A is closed) may act as the master, transmitting itspairing key to device 20D. Once device 20D has the key, it may act asmaster to device 20E.

Reference is now made to FIG. 4, which is a flow chart illustration of aset up to the pairing operation, performed by PLC devices 20 of thepresent invention. The pairing itself may be implemented through astandard pairing operation, such as the UKE (Unicast Key Exchange)protocol in HPAV. Upon power up (step 30), which occurs when each device20 is first plugged in, or upon a change in the pairing circuit state,PLC unit 22 may check the output of pairing circuit 24. If the unit isunpaired (i.e. if pairing circuit 24 indicates that both switches 26 areopen) as checked in step 32, then this indicates that the current device20 is the first device of the network and thus, it may become the“master” of the new network. In which, case, PLC unit 22 may generate(step 34) a default key, which may be a unique encryption key based onthe MAC (media access control) address of the PLC unit 22, and may storeit, such as in storage unit 23. This may become the active key for thenetwork. When PLC unit 22 may be re-plugged into the outlet (such asafter power down), it may use the active key that is stored in itsstorage unit 23.

In step 36, the pairing mode is checked. If PLC unit 20 is the master(i.e. only micro switch 26A is closed, indicating an inner unit), PLCunit 20 may transmit (step 38) its network key (stored in key storageunit 23) to the unit currently paired to it during the pairing protocol.In one embodiment, the master may transmit the network key signal with alow power signal, directly between the units. The power level may besuch that a unit that is far enough away (over 1 meter) will not be ableto hear the signal. Even though the pass-through filter is designed toremove the PLC signals, since the two PLC units are so physically close,the network key signal may be strong enough that the filter cannotfilter it out.

In another embodiment, the master may transmit a regular transmission,at a standard power level. This embodiment may assume that all of theunits in the home network utilize the sensing mechanism describedhereinabove and thus, may process the transmission of the key only whenthe sensing mechanism indicates that the unit is currently paired. Evenif units on neighboring networks receive the transmission, they will notbe able to decode it if they are not currently paired.

If PLC unit 20 is in the middle (i.e. both micro switches 26A and 26Bare closed), then PLC unit 20 may listen (step 40) for the transmissionof the key from the master unit during the pairing protocol and maystore (step 42) the received key in its storage unit 23 once it has beenreceived. This becomes its network encryption key, overriding itsdefault key. Since PLC unit 20 is in the middle, it may also transmit(step 44) the newly received key to the next unit, during a secondpairing protocol.

If PLC unit 20 is a slave unit (i.e. only micro switch 26B is closed,indicating an outer unit), then PLC unit 20 may listen (step 46) for thetransmission of the key from the middle unit during the pairing protocoland may store (step 48) the received key.

It will be appreciated that, when the A sensor is activated, PLC unit 20may act to transmit the key while when the B sensor is activated, PLCunit 20 may act to receive the key. PLC units 20 may ensure that theyreceive the key before transmitting it.

It will be appreciated that the procedure described hereinabove is userfriendly. The user merely has to plug the master into an outlet and thento plug the remaining PLC units into the master. There are no timingrequirements and no requirements to depress a switch.

It will be appreciated that the entire process comprises the followingsteps:

Connecting the units to the power network and to each other.

Pairing detection: the units may detect that they are attached.

Type recognition: each unit may recognize whether it is a inner unit, amiddle unit or an outer unit.

Communication: the unit with A sensing unit active may communicate theactive key to the unit with the B sensing unit active.

Setting: the unit with the B sensing unit active may overwrite its keywith the received active key.

In another embodiment, a user may connect PLC units 20 together beforeplugging them into wall socket 18. PLC units 20 may power up at the sametime and may determine if they are an inner, outer or middle unit. Theinner unit may transmit the key and the middle and outer units may hearthe transmission, all at generally the same time. Since the middle andouter units may have the B sensing unit active, they may wait until theyenter the pairing protocol to receive the key. This embodiment mayrequire that the transmission from the inner unit be of full power.

Reference is now made to FIG. 5, which illustrates an alternativeembodiment of the present invention which also provides physical pairingof the devices, resulting in hands-free pairing of the devices. Thisembodiment may be simple, intuitive and secure and may require noadditional hardware or user-interface elements. As a result, it may besuitable for retail and self-installation.

In FIG. 5, network devices 60 may be HPAV bridges or other devicesconnectable over some physical medium 62. For example, HPAV bridges areconnectable over a powerline, while Bluetooth devices are connectableover the air. It is over physical medium 62 that devices 60 normallycommunicate. For powerline networks, devices 60 typically comprise PLCunit 22 and key storage unit 23.

In addition to physical medium 62, most networking devices also have adata connector, such as data connector 15, with which they connect tosome data processing device, such as computing device 19 (FIG. 1B). Forexample, data connector 15 may be an Ethernet connector, connecting toan internal Ethernet port. In accordance with a preferred embodiment ofthe present invention, devices 60 may utilize an Ethernet cable 64 toconnect together and to initiate the pairing protocol. In accordancewith a preferred embodiment of the present invention, devices 60 mayimplement the pairing protocol over physical medium 62.

It will be appreciated that the topology of FIG. 5 is normally invalidin real-world networks since such a topology creates a loop in thenetwork. However, in the present invention, PLC unit 22 may detect theloop created by cable 64 and may use its presence to identify that it ispossible to initiate the pairing process.

Each PLC unit 22 may detect the presence of the loop in any suitablemanner. For example, it may receive the MAC (media access control)address of the other device 60 twice, once from the powerline networkand once from cable 64 (sent from the other device 60). In anotherexample, one device 60 may send a packet along cable 64 to the otherdevice 60 that only another device 60 is capable of parsing; computingdevice 19, which may normally be connected via connector 15, may beincapable of parsing such a packet.

In accordance with a preferred embodiment of the present invention, thecommunication channel created over cable 64 may be used to passinformation useful to the pairing process directly between devices 60.As a result of the back channel created over cable 64, the pairingprocess may be more secure.

It will be appreciated that, as is common for most Ethernet connectors,data connector 15 may include a sensing unit 66 which may sense whencable 64 is connected therein. Sensing unit 66 may indicate such to PLCunit 22 which, when receiving such a signal, may initiate the pairingprotocol.

For example, the embodiment of FIG. 5 supports pairing over physicalmedium 62 using a version of a standard protocol, such as the UKE(Unicast Key Exchange) protocol in HPAV. In such protocols, one deviceenters into an “add-state” in which it is prepared to acceptpairing/join requests, while the second device enters into a“join-state” in which it requests to pair or join the network. When thenetwork is in a state where one device is in add-state and anotherdevice is in join-state, the pairing occurs over the physical mediumusing a key exchange protocol.

In the present invention, the standard protocols may be extended byexploiting the additional communication channel provided by cable 64. Inthis extended model, shown in FIG. 6 to which reference is now made, onedevice 60, for example, device 60B, first detects (step 70) that it isnot part of an existing network. When device 60B may detect a “LinkUpEvent” indicating that its Ethernet link has come up (i.e. cable 64 hasbeen plugged into its data connector 15), this may trigger the start ofa pairing process, where the initial phases of the pairing may beperformed over cable 64.

Device 60B may issue (step 72) an AddJoin.Req message through its dataconnector 15, specifying in the message its identity (e.g. its sourceaddress). Device 60A, upon receiving the request, may enter (step 74)into the add-state and may record (step 76) the identity of the devicethat triggered the pairing process. Device 60A may respond to device 60Bwith a confirmation message (AddJoin.Cnf) through its data connector 15.

Device 60A may now wait for the appearance of a “Join.Req” message overphysical medium 62. In step 78, device 60B may enter the join-state andmay issue the Join.Req message over physical medium 62.

Since, in the present invention, device 60A may know the identity ofdevice 60B, which is requesting to join, when device 60A receives theJoin.Req message, it may verify (step 80) that the device sending therequest over physical medium 62 is the same device that triggered theinitiation of the pairing process over cable 64. If the devicerequesting to join is not the same device, device 60A may reject thepairing request. Otherwise, the two devices may enter the standard keyexchange protocol (step 82) such that device 60B may receive (step 84)the network key. The pairing process typically may terminate once adevice joins the network or after a timeout period.

It will be appreciated that, since device 60A may verify the devicerequesting the pairing, the process may be more secure and may ensurethat devices outside the network cannot unintentionally join.

In an alternative embodiment, devices 60A and device 60B may finalizethe pairing process by passing the network key along cable 64 ratherthan along physical medium 62.

It will be appreciated that cable 64 may be utilized to pairnon-powerline devices as well. For example, any medium where security isrequired, such as wireless, Bluetooth, etc, and where the devices havedata connectors, similar to data connectors 15, in addition to thecommunication along their physical medium, may implement the keyexchange protocol described hereinabove using cable 64.

While certain features of the invention have been illustrated anddescribed herein, many modifications, substitutions, changes, andequivalents will now occur to those of ordinary skill in the art. It is,therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the invention.

1. A method of pairing power line communication devices, the methodcomprising: sensing a physical connection with a second said device,said physical connection being other than via a powerline medium;entering an appropriate pairing state upon sensing said physicalconnection, said pairing state being either an add device state or ajoin device state; and performing pairing with said second device. 2.The method according to claim 1 and wherein said physical connection isa data cable.
 3. The method according to claim 2 and wherein saidsensing comprising sensing the connection of said data cable and theconnection of said second device also to said data cable.
 4. The methodaccording to claim 2 and also comprising said device in said join devicestate passing an identifier to said device in said add state over saidcable and said device in said add state agreeing to said performing onlywith a device having said identifier.
 5. The method according to claim 1and wherein said physical connection is a pass through power connection.6. The method according to claim 5 and wherein said entering compriseseach said device sensing if the device is closer or further from a wallsocket than another device and devices not connected to said wall socketreceiving a network key at least from a device connected to said wallsocket.
 7. A power line communication device comprising: a power linecommunication unit; a sensor to sense a physical connection to a secondpower line communication device other than via a powerline medium; and apairing unit to receive an indication of a physical connection betweensaid power line communication device and said second power linecommunication device and to initiate a pairing process with said secondpower line communication device.
 8. The device according to claim 7 andwherein said sensor is an Ethernet link sensor and wherein said physicalconnection is via an Ethernet cable.
 9. The device according to claim 8and wherein said pairing unit comprises a data unit to pass a deviceidentifier, if said device is in a join device state, or to receive adevice identifier if said device is in an add state along said Ethernetcable.
 10. The device according to claim 7 wherein said powerlinecommunication device also has a pass-through power connection andwherein said sensor is an inner sensing unit at an inner location ofsaid device to sense if said device is plugged in and an outer sensingunit at an outer location of said device to sense if a second power linecommunication device is plugged into said device wherein said power linecommunication unit comprises a network key unit to control a network keyas a function of which of said switches is activated.
 11. The power linecommunication device according to claim 10 and wherein said network keyunit comprises a receiver to receive a network key when said innersensing unit is activated and a transmitter to transmit said network keywhen said outer sensing unit is activated.
 12. The power linecommunication device according to claim 10 and also comprising a socketand a plug, wherein said inner location is underneath a surface of saidsocket and wherein said outer location is underneath a surface of saidplug.
 13. The power line communication device according to claim 10 andwherein said sensing units are proximity sensors.
 14. The power linecommunication device according to claim 13 and wherein said proximitysensors are one of the following types of sensors: electrical proximitysensors, reed switches controllable by magnets and micro switchesdepressed by mechanical pressure.
 15. The power line communicationdevice according to claim 10 and wherein said sensing units aretransmission sensors.
 16. The power line communication device accordingto claim 10 and wherein said transmission sensors are one of thefollowing types of sensors: RFID units and coils that receive andtransmit.
 17. The power line communication device according to claim 10and wherein two or more units are connectable together.
 18. A method ofpairing communication devices which communicate along a non-data-cablemedium, the method comprising: sensing a data cable connection with asecond said device; entering an appropriate pairing state upon sensingsaid data cable connection, said pairing state being either an adddevice state or a join device state; and performing pairing with saidsecond device along said non-data-cable connection.
 19. A method ofpairing power line communication devices, the method comprising: havingsaid devices incorporated into pass-through devices; plugging a firstsaid pass-through device into a wall socket and at least a second saidpass-through device into said first device; and unplugging said devicesfrom said socket and from each other after pairing has occurred.
 20. Themethod according to claim 19 and wherein said plugging comprisesconnecting said first and at least said second two devices togetherprior to plugging said combination into said wall socket.
 21. The methodaccording to claim 19 and wherein said plugging comprises connectingsaid devices one at a time.